1. Field of the Invention
This invention relates generally to the field of semiconductor device manufacturing and, more particularly, to a method and apparatus for dynamic adjustment of a sensor sampling rate.
2. Description of the Related Art
To fabricate a semiconductor device, a wafer is typically provided to numerous processing tools in a predetermined sequence. The processing tools may include photolithography steppers, etch tools, deposition tools, polishing tools, rapid thermal processing tools, implantation tools, and the like. Each processing tool modifies the wafer according to a particular operating recipe. For example, a photolithography stepper may be used to form a patterned layer of photoresist above the wafer. Features in the patterned layer of photoresist correspond to a plurality of features, e.g. gate electrode structures, which will ultimately be formed above the surface of the wafer. The tool sequence, as well as the recipes used by the tools, must be carefully controlled so that the features formed on the wafer meet appropriate design and performance criteria. Thus, advanced process control (APC) systems are often used to coordinate operation of the processing tools.
A conventional APC system includes one or more machine interfaces that are communicatively coupled to equipment interfaces associated with each of the processing tools. The machine and equipment interfaces are typically computers or workstations that are coupled to a network. For example, a plurality of processing tools may be coupled to an Intranet via an associated plurality of equipment interfaces. A machine interface that implements the conventional APC system may also be coupled to the Intranet. In operation, the conventional APC system initiates a control script based upon a manufacturing model, which can be a software program that automatically retrieves the data needed to execute a manufacturing process, and transmits one or more control messages, such as the operating recipe, to the processing tools.
The processing tools may include one or more sensors to collect data associated with operation of the processing tool. For example, an etching tool may include a sensor to monitor the radio frequency power delivered by the etching tool. For another example, a rapid thermal anneal tool may include a thermocouple to monitor a temperature within the tool. The data acquired by the various sensors may be referred to as trace data. The collected tool trace data may then be provided to the APC system, which may use the collected tool trace data for various purposes such as fault detection and/or classification. For example, the tool trace data collected by the thermocouple in the rapid thermal anneal tool may indicate that the temperature within the tool has dropped below a desired threshold, indicating a possible fault.
The network that is used to transmit control messages, tool trace data, and any other information between the APC system and the processing tools has a finite bandwidth. Consequently, it is not generally possible to continuously collect and transmit tool trace data using all the sensors in all the processing tools coupled to the network. For example, an exemplary APC system may be coupled to several processing tools, each of which may have as many as 50 or 60 associated sensors. If all of the sensors continuously attempted to provide tool trace data over the network, the network would become overloaded and unable to transmit the collected tool trace data. Accordingly, the APC system provides a predetermined data collection plan that specifies which sensors may collect tool trace data and a sampling rate associated with each sensor. For example, a sensor may have a sampling rate of about one Hertz.
Although the predetermined data collection plan may be adequate when the processing tools are operating normally, the predetermined data collection plan may limit the ability of the APC system to detect and/or classify faults or other unexpected events associated with the processing tools. For example, tool trace data from a sensor may deviate from an expected value, which may indicate a fault associated with the tool. Thus, it may be desirable to increase the sampling rate of the sensor to provide additional data that may assist in detecting and/or classifying the suspected fault. Moreover, it may also be desirable to decrease the sampling rate of one or more other sensors to provide additional network bandwidth for the high sampling rate sensor. However, conventional APC systems are not able to modify the predetermined data collection plans to respond to changing conditions and/or bandwidths.
The present invention is directed to addressing the effects of one or more of the problems set forth above.